Pipelines are used to transport oil, gas, and the like, e.g. from oil rigs to the shore. Such oil fluid contains constituents of water, and since the pipelines lie on the sea-bed covered by water, the ambient temperature may result in a cooling of the oil fluid to such an extent that the water constituents precipitate as ice on the inside wall of the pipeline. The precipitated ice may, at least partly, block the flow in the pipelines, thus decreasing the velocity of the oil fluid.
Furthermore, the water constituents in the oil may comprise alkaline earth cations and anions, and water-insoluble scales are formed when cations and anions are present in a certain concentration.
In order to remove such ice and scales, pipeline pigs are inserted into the pipeline to loosen and brush off the ice and scales. However, the insertion of such pipeline pigs in the oil fluid is a very complicated process and, in the event that the pipeline pigs get stuck due to a blockage in the pipeline, the pipeline pigs are not easily retracted from the pipeline again.
Thus, there is a need for a tool which can move forward in a blocked pipeline in order to retract the pipeline pigs again and/or clean the pipeline.